This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A054901 #10 Feb 18 2021 02:33:10
%S A054901 1,4,10,16,25,40,64,100,160,250,256,400,625,640,1000,1024,1600,2500,
%T A054901 2560,4000,4096,6250,6400,10000,10240,15625,16000,16384,25000,25600,
%U A054901 40000,40960,62500,64000,65536,100000,102400,156250,160000,163840
%N A054901 Numbers of the form 2^i*5^j where i+j is even.
%C A054901 m is in the sequence iff m/10 is already in the sequence or m is a power of 4 or 25.
%H A054901 Amiram Eldar, <a href="/A054901/b054901.txt">Table of n, a(n) for n = 1..10000</a>
%F A054901 Sum_{n>=1} 1/a(n) = 55/36. - _Amiram Eldar_, Feb 18 2021
%t A054901 max = 200000; Reap[Do[k = 2^i*5^j; If[k <= max && EvenQ[i + j], Sow[k]], {i, 0, Log[2, max] // Ceiling}, {j, 0, Log[5, max] // Ceiling}]][[2, 1]] // Union (* _Amiram Eldar_, Feb 18 2021 after _Jean-François Alcover_ at A036667 *)
%Y A054901 Intersection of A028260 and A003592.
%Y A054901 Cf. A000302, A009969, A054774.
%K A054901 easy,nonn
%O A054901 1,2
%A A054901 _Henry Bottomley_, May 23 2000